60 PHYSIOLOGY AT THE FARM. 



of blood, covered with a peritoneal coat, and of a mottled blue 

 or purplish grey colour. It seldom exceeds three pounds in 

 weight. In the horse it has a pyramidal form ending in a 

 point. It has no excretory duct. It is largely provided with 

 blood-vessels, nerves, and lymphatics. The spleen has a proper 

 coat beneath the external peritoneal covering. This internal 

 coat, the proper tunic, is thicker and stronger than the serous 

 coat, and covers the entire surface of the organ. It is of a 

 whitish colour, and consists of interlaced fasciculi of areolar 

 tissue, mixed with a fine elastic substance. In addition to 

 these there are pale soft fibres having the appearance of 

 unstriped muscular fibres. The proper tunic cannot be de- 

 tached from the spleen, because prolongations pass from it 

 into the substance of the organ. This coat also, at the hilum 

 or point where the vessels enter and issue, is reflected inwards, 

 forming elastic sheaths or canals in which the large blood- 

 vessels and nerves, and their chief branches, are supported. 

 A number of small elastic bands stretch across in every direc- 

 tion between these sheaths and through the intermediate 

 substance of the spleen, which are named trabeculce, or little 

 beams. The inner coat is the origin of all that elastic frame- 

 work running through the spleen. There is contained in this 

 framework, besides the vessels and nerves, a peculiar red 

 pulpy substance with which the tufts or pencils of capillary 

 vessels lie in contact, supported by microscopic trabeculse 

 running through the pulp in all directions. The pulp itself 

 lies altogether outside the vessels between the branches of the 

 venous plexus. It consists of numerous rounded granular 

 bodies which have a reddish colour, and are about the size of 

 the blood-corpuscles. Their cohesion is very slight, and the 

 terminal tufts of the arterial system spread out amongst them. 

 In the substance of the spleen, elongated caudate corpuscles 

 are seen in considerable numbers. There are also round 



